Third quarterback rule
The third quarterback rule was a rule in the National Football League that governed the use of a third quarterback in addition to the starter and the backup. This rule was abolished in the 2011 season, when the NFL increased the roster size to allow 46 players to dress for a game.
The third quarterback did not count towards the team's 45-man active roster. If the third quarterback entered the game at any position during any of the first three quarters, the starter and backup became ineligible to play for the rest of the game; the third quarterback could have entered the game in the fourth quarter while preserving the eligibility of the starter and backup.
The full text of the rule was:
Teams will be permitted an Active List of 45 players and an Inactive List of eight players for each regular-season and postseason game. Provided that a club has two quarterbacks on its 45-player Active List, a third quarterback from its Inactive List is permitted to dress for the game, but if he enters the game during the first three quarters, the other two quarterbacks are thereafter prohibited from playing.
Although it is not specifically indicated, the NFL had interpreted its rule to mean that in order to designate a third quarterback, the two on the active roster must both be "bona fide" quarterbacks, not other position players merely designated as quarterbacks.
The third quarterback rule was instituted for the 1991 NFL season in reaction to a 1990 game between the Washington Redskins and Philadelphia Eagles. In that game—sometimes called "The Body Bag Game"—Redskins lost both starting quarterback Jeff Rutledge and backup Stan Humphries to injuries. Without a third quarterback on their active roster, Washington had to either use a different player for that position or forfeit the game. Brian Mitchell, a running back who played quarterback in college, completed the game in the quarterback position. The Redskins lost to the Eagles, 28-14.
The rule was abolished for the 2011 season. There is now no third quarterback exception and the active roster has been increased from 45 to 46.
In the 2010 NFC Championship Game between the Green Bay Packers and Chicago Bears, the rule was triggered with 57 seconds left in the third quarter. The Bears' starting quarterback, Jay Cutler, suffered from an MCL sprain just after halftime. His replacement, Todd Collins, was pulled after throwing four poor passes including two near interceptions. When Caleb Hanie, the Bears' designated third quarterback entered the game before the fourth quarter, it meant that the Bears could not return either Cutler or Collins to the field the rest of the game. The Packers won the game, 21-14. 
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